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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Neuropeptides were directly detected in single identified neurons and the neurohemal area of peptidergic (neuroendocrine) systems in the Lymnaea brain by using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The samples were placed in matrix solution and ruptured to allow mixing of cell contents with the matrix solution. After formation of matrix crystals, the analytes were analyzed by MALDI-MS. It was surprising that clean mass spectra were produced, displaying extreme sensitivity of detection. In one of the neuroendocrine systems studied, we could demonstrate for the first time, by comparing the peptide patterns of soma and of neurohemal axon terminals, that processing of the complex prohormone expressed in this system occurs entirely in the soma. In the other system studied, novel peptides could be detected in addition to peptides previously identified by conventional molecular biological and peptide chemical methods. Thus, complex peptide processing and expression patterns could be predicted that were not detected in earlier studies using conventional methods. As the first MALDI- MS study of direct peptide fingerprinting in the single neuron these experients demonstrate that MALDI-MS forms a new and valuable approach to the study of the synthesis and expression of bioactive peptides, with potential application to single-cell studies in vertebrates, including humans.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 16 (1999), S. 695-701 
    ISSN: 1573-904X
    Keywords: capillary zone electrophoresis ; high performance liquid chromatography ; isotachophoresis ; mass spectrometry ; proteins ; degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Capillary zone electrophoresis with isotachophoretic sample preconcentration (ITP-CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection and on-line coupling to electrospray-ionization mass spectrometry were investigated for their potential to separate and identify fragments of recombinant human interleukin-6 formed during acidic stress of the parent protein. Results. Based on the orthogonal separation principles governing ITP-CZE and RP-HPLC, different peak patterns were observed using both methods. The selectivity of ESI-MS allowed identification of several co-migrating compounds. Data obtained by on-line ESI-MS were compared to results from off-line investigations by MALDI-TOF-MS performed with single fractions collected from the RP-HPLC system. Cleavage of the protein backbone occurred preferably at acid-labile Asp-sites. The total amount of rhIL-6 needed for ITP-CZE-ESI-MS identification of all fragments was only in the upper femtomole range, while RP-HPLC required amounts of protein three orders of magnitude higher. On the other hand, the low CE sample volume opposes the collection of fractions to perform off-line analysis. Conclusions. Growing acceptance of CE with on-line MS detection for pharmaceutical quality control of proteins is expected.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 25 (1988), S. 806-810 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair chromatography ; Valve switching ; Fluorouracil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorouracil has been analyzed with a reversed-phase ion-pair liquid chromatographic system applying PRP-1 as the stationary phase. A valve switching technique was applied for the separation of the analyte and some other chemotherapeutic agents. The described procedure gives a rapid screening for the analyte in urine and plasma samples without interferences from late eluting solutes. Biological samples are pretreated by means of a liquid-liquid extraction resulting in a recovery of about 52% for plasma and urine with minimum detectable amounts of about 5ng/ml. The sensitivity and the selectivity of the procedure allows the monitoring of fluorouracil in body fluids and subsequent pharmaco-kinetic studies of the fluoropyrimidine.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 66 (1994), S. 4295-4301 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary columns ; Mass spectrometry ; Autoderivatization ; Cyclophosphamide ; 4-Ketocyclophosphamide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The selectivity of a capillary gas chromatographic assay for the anti-neoplastic and immunosuppressive agent cyclophosphamide (CPA) towards one of its naturally occurring metabolites, i.e. 4-ketocyclophosphamide (4-keto CPA), has been studied. Mass spectrometry studies showed that a cyclization product of 4-keto-CPA can form using the same chromatographic conditions as those under which CPA was determined. However, the amount produced is relatively small (less than 10%) compared with the percentage produced from CPA. Furthermore, both cyclization products, formed by loss of HCI and intraalkylation of the parent compounds, can be separated well under suitable chromatographic conditions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Intact glucosinolates are separated and identified in standard mixtures and in plant extract of Brussels sprouts by using the liquid chromatography frit to fast-atom bombardment mass spectrometry technique. The separation of the individual glucosinolates is achieved by using a conventional-bore high-performance liquid chromatography column with an aqueous ammonium acetate - acetonitrile gradient. The mandatory flow-rate reduction is achieved by using a pneumatic splitter. The determination limits are estimated to be below 20 μg/g in plant material for various glucosinolates using the sample pretreatment described.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new, attractive application of the phase-system switching (PSS) technique is demonstrated. The PSS system is used in combination with liquid chromatography coupled to continuous-flow fast-atom bombardment mass spectrometry (LC/CF-FABMS) to achieve flow-rate reduction from 1.0 mL/min in the high-performace liquid chromatography (HPLC) system to 15μL/min going into the mass spectrometer. In PSS, a compound of interest, in this case erythromycin 2′-ethylsuccinate, is enriched after the analytical separation, on a short trapping column, from which it is desorbed subsequently to the LC/MS interface. Optimal mobile phases and flow-rates can be used for the HPLC separation as well as for the mass spectrometric detection. Desorption of the analyte is achieved either by using a flow-rate of 15 μL/min without a splitter or a flow-rate of 230 μL/min with a splitter. Compared to the LC/CF-FAB MS methods using a conventional bore HPLC column and a splitter, improved detection limits for the model compound were achieved using the PSS method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 643-647 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary Gas Chromatography (CGC) is capable of determining underivatized cyclophosphamide (CPA) using SCOT OV 275 columns. Then CPA is subjected to in situ degradation resulting in formation of a cyclization product which can be determined selectively in biological fluids. In routine bioanalysis however cyclization products of CPA metabolites might interfere, e.g. 4-keto CPA. In the present study possible formation of cyclization products of 4-keto CPA similar to CPA was monitored by Mass Spectrometry. Cyclization of 4-keto CPA in situ was demonstrated to occur, resulting in a product similar to that of CPA. Both cyclization products could be determined selectively and it appeared that in situ cyclization of 4-keto CPA was negligible (〈5%), probably owing to extra stabilization of the CPA metabolite by keto-enol tautomerism as has been demonstrated by NMR.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-739X
    Keywords: Blood pressure ; Enalapril ; Kidney function ; Kininase 11 ; Natriuresis ; Renin-angiotensin system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pharmacy world & science 10 (1988), S. 200-206 
    ISSN: 1573-739X
    Keywords: Administration, intravenous ; Administration, oral ; Biological availability ; Clinical trials ; Cyclophosphamide ; Drug interactions ; Fluorouracil ; Methotrexate ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyclophosphamide was administered to 12 breast cancer patients in combination with methotrexate and fluorouracil. Doses prescribed were cyclophosphamide 75 mg/m2, methotrexate 30 mg/m2 and fluorouracil 500 mg/m2 (per square meter body surface). Cyclophosphamide was administered intravenously and orally in aqueous solutions and in tablets in a randomized cross-over trial. Methotrexate and fluorouracil were administered intravenously, methotrexate was given first and then fluorouracil. Assays of cyclophosphamide in blood plasma were performed by capillary gas chromatography. Data of mean bioavailability of cyclophosphamide administered by tablets were suggestive of sufficient absorption. In 2 patients, however, a lower bioavailability of cyclophosphamide was demonstrated. Intra-individual differences in the terminal slope of the plasma decay curves after intravenous and oral administration in some patients decreased the calculated bioavailability of cyclophosphamide, if these values were included in the calculation of cyclophosphamide bioavailability. Compared with the administration of the solutions peak times, lag-times and mean absorption times of cyclophosphamide given in tablets were markedly prolonged. It is concluded that interactions between cyclophosphamide and methotrexate and/or fluorouracil after oral dosing as tablets are different from interactions observed after intravenous administration of cyclophosphamide.
    Type of Medium: Electronic Resource
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